Bronchoreactive ("asthmatic") and non-bronchoreactive ("nonasthmatic") dog populations will be defined by means of aerosol Ascarus antigen challenge. Strips of trachealis smooth muscle from dogs in both groups will be studied and compared in terms of motility and biochemical responses to a variety of spasmogenic and relaxant agents. Isometric tension, cyclic nucleotides and protein kinase activity will be determined as a function of dose of agonist and time of agonist exposure. We will be looking for increased responsiveness to spasmogens and/or decreased responsiveness to relaxants in the asthmatic groups. Correlations of biochemical and functional motility changes will be done in order to test present hypotheses and generate new hypotheses of asthma. Interactions of prostaglandin synthesis inhibitors with contractile and relaxant agonists will be studied to determine whether prostaglandin synthesis or sensitivity is involved in differences between asthmatic and nonasthmatic groups. Adenylate cyclase and phosphodiesterase will be studied to determine whether differences between groups are due to identifiable enzymatic differences.